Method and bending device for bending a sheet metal part

ABSTRACT

In a method for bending a sheet-metal part ( 50 ) on a profile body ( 24 ) having a bending profile ( 52 ), the sheet-metal part ( 26, 28 ) is pressed against the profile body ( 24 ) at an initial contact point ( 54 ), wherein bending rollers ( 26, 28 ), starting from the initial contact point ( 54 ), press the sheet-metal part ( 50 ) along the bending profile ( 52 ) against the profile body ( 24 ) and adapt it plastically to the shape of the profile body ( 24 ). Furthermore, a bending device ( 22 ) for carrying out the method is specified.

The invention relates to a method for bending a sheet metal part on aprofile body comprising a bending profile and a bending device forcarrying out the method.

For forming a sheet metal part it has been hitherto usual to give adesired shape to the sheet metal part by stamping or pressing togetherprofile bodies. For example, the sheet metal part according to DE 39 40984 A1 is positioned between two identical profile bodies comprisingbending profiles, which may be moved together in a fitting manner on thebending profiles in the manner of two articulated pieces. The sheetmetal part located between the profile bodies is formed by pressingtogether the profile bodies according to the shape of the bendingprofiles. The forming process consists in that the sheet metal part isfitted, piece by piece, to the shape of the bending profiles of theprofile bodies.

A comparable forming method is known from the publication EP 0 530 956A1. By pressing together the profile bodies, compressive stresses areproduced between the profile bodies and the sheet metal part at pressurepoints where the profile bodies are applied to the sheet metal part. Asthe sheet metal part is only applied at comparatively few pressurepoints by pressing together the profile bodies for forming, but is notguided over an entire bending region of the sheet metal part by thebending profiles of the profile bodies, it leads to uneven distributionof the compressive stresses and thus to uneven forming of the sheetmetal part, including deviations of shape such as, for example,undesired buckling of the sheet metal part.

Thus, such a forming method for forming, for example, a bearingconfigured from a sheet metal part is also unsuitable as a seat platefor a piston roller of a radial piston engine according to thepublication DE 198 10 372 A1. A cross section through a cylinder block 2of the radial piston engine is shown in FIG. 5 and a cross sectionthrough a cylinder 4 according to FIG. 5 is shown in FIG. 6. In theradial piston engine, pistons 6 are radially arranged perpendicular to adrive shaft 8, the stroke of the pistons 6 being carried out in theradial direction 10 (only indicated by reference numerals in FIG. 6)relative to the drive shaft 8 by an external stroke ring 12. The bearing14 is positioned between the piston 6 and a piston roller 16 coupledthereto and serves as a seat plate on the piston side for the pistonroller 16 which may be rotated in a rotational axis 18 oriented parallelto the drive shaft 8, illustrated in dotted lines in FIGS. 5 and 6which, when rotating the drive shaft 8, rolls along an inner face 20 ofthe stroke ring 12. Deviations in shape on the seat plate lead, duringthe operation of the radial piston engine, to material wear on thepiston roller 16 and also on the seat plate itself, denoted as a bearing14, as well as possibly to resultant wear to the stroke ring 10.

The object of the invention is to provide a method for bending a sheetmetal part on a profile body comprising a bending profile, and a bendingdevice for carrying out the method, by means of which the shape of thesheet metal part may be adapted particularly accurately to the shape ofthe profile body, relative to the bending profile of the profile body,as a result of bending stresses exerted particularly uniformly on thesheet metal part and as a result of particularly material-protectingforming.

Relative to the method, the aforementioned object according to theinvention is achieved by the features of claim 1. Advantageousdevelopments form the subject of the sub-claims referring back thereto.

Relative to the device, the aforementioned object is achieved accordingto the invention by the features of claim 6. Advantageous developmentsform the subject of the sub-claims referring back thereto.

Thus, the bending device for bending a sheet metal part, in order toadapt said sheet metal part to a bending profile of a profile bodyprovided therefor, comprises bending rollers, whereby the sheet metalpart may be pressed against the profile body at an initial contact pointprovided on the profile body and may be formed along the bending profileof the profile body. The bending rollers are, in turn, mounted on acarriage which is configured to be able to be lifted at an adjustabledistance from the profile body. The bending rollers are connected to oneanother in the manner of a tension spring.

The method for bending the sheet metal part initially comprises pressingthe sheet metal part by means of the bending rollers at the initialcontact point of the profile body and subsequently thereto an adaptationof the sheet metal part to the bending profile of the profile body byplastic forming of the sheet metal part, for which the bending rollerspress the sheet metal part along the bending profile proceeding from theinitial contact point.

The initial contact point, in this case, is understood to be thepointed, linear or planar portion of the profile body against which thesheet metal part is pressed before the start of the bending process onthe profile body.

The bending of the sheet metal part is always carried out by localplastification at contact points at which the bending rollers applycompressive stress to the sheet metal part. The compressive stress isproduced, on the one hand, by lifting the carriage in the direction ofthe profile body between the respective bending roller and the sheetmetal part and, on the other hand, by the connection of the bendingrollers in the manner of a tension spring, whereby one bending roller isacted upon by a further bending roller connected thereto in the mannerof a tension spring with a tractive force and in the direction thereof,which at the contact point of the bending roller with the sheet metalpart acts on the sheet metal part as compressive stress.

The advantages achieved by the invention are, in particular, that bypressing the sheet metal part against the profile body during thebending process, the sheet metal part is fixed and there is no relativemovement between the sheet metal part and the profile body, whereby thebending process is carried out relatively inaccurately and an elementprovided on the bending device or the sheet metal part would be affectedin a manner which might damage the material, such that the shape of thesheet metal part might deviate from that of the bending profile of theprofile body. Moreover, a local plastification at the contact pointsbetween the bending rollers and the sheet metal part is achieved overthe entire sheet metal part, including the sheet metal part ends,provided for the forming, by the compressive stress generated by theconnection of the bending rollers in the manner of a tension spring,combined with the compressive stress generated by lifting the carriage,acting on the sheet metal part. Moreover, the sheet metal part is guidedby bending rollers in continuous contact from an initial contact pointalong the bending profile on the profile body in the manner of a rollingbending method, as a result of which the shape of the sheet metal partis, furthermore, identical to the bending profile of the profile body.With the continuous guiding of the sheet metal part during the bendingprocess, moreover, buckling of the sheet metal part, which would have adamaging effect on the material, is avoided. Moreover, as a result ofthe method according to the invention and the bending device accordingto the invention, the material properties of the sheet metal part areaffected to a comparatively small extent.

According to an advantageous embodiment, the compressive stress betweenthe bending rollers and the sheet metal part produced by lifting thecarriage and the compressive stress between said bending rollers and thesheet metal part produced by the connection of the bending rollers inthe manner of a tension spring, are related to one another such thatbending stresses exerted by the bending rollers on the sheet metal partduring the bending process for plastic forming of the sheet metal partare approximately uniform over the entire bending profile of the profilebody.

According to an advantageous embodiment, the bending rollers are mountedon a carriage such that lifting the carriage moves the bending rollerstowards the sheet metal part and presses said metal part against theprofile body and fixes said sheet metal part thereto. As a result, anadditional fixing device for fixing and securing the sheet metal partduring the bending process is not required.

Expediently, the bending rollers on the carriage are rotatably mountedon a single axis such that a further lifting of the carriage, resultingfrom pressing the sheet metal part against the profile body, causes thebending rollers to roll along the bending profile of the profile body onthe sheet metal part, and to press said sheet metal part against theprofile body and to form said sheet metal part plastically, such thatthe sheet metal part adopts the shape of the bending profile of theprofile body. By rolling the bending rollers along the sheet metal partby further lifting of the carriage, the contact of the bending rollerswith the sheet metal part during the bending process is maintaineduninterrupted, whereby a particularly uniform bending process isachieved.

In order to make the shaping of the sheet metal part accurate, it isexpedient to lift the carriage in a continuous, uninterrupted bendingprocess, comprising only one step, in the direction of the profile body,both for pressing the sheet metal part against the profile body and forforming the sheet metal part.

In order to design the bending device particularly simply andcost-effectively, the carriage for carrying the bending rollers is ofplate-shaped design and provided at a vertical distance parallel to thesheet metal part.

In an expedient development, the carriage is dimensioned with a largesurface area such that, by lifting the carriage, the bending rollerswhich are rotatable on a single axis and displaceably mounted onsupports on the carriage, follow a path of the bending profile on theprofile body for bending the sheet metal part in a particularly accuratemanner.

In order to form the sheet metal part according to the bending profileof the profile body and to avoid a relative movement between the profilebody and the sheet metal part, it is expedient to fix the profile bodyfor the bending process.

Moreover, it is expedient to provide on the bending device a countersupport which assists the bending process such that the sheet metal partis already fixed to the profile body before the start of the bendingprocess and is secured to the counter support to avoid relativemovements between the sheet metal part and the profile body during thebending process, in addition to pressing by the bending rollers.

The counter support is expediently arranged on the carriage and pressesthe sheet metal part by lifting the carriage at the initial contactpoint towards the profile body. As a result, for example, at the initialcontact point the sheet metal part is prevented from being forced awayby compressive stresses exerted by the bending rollers on the sheetmetal part.

In an expedient development, the counter support is connected to thecarriage in the manner of a compression spring such that, after pressingthe sheet metal part against the profile body by means of the countersupport, a further lifting of the carriage for forming the sheet metalpart by means of the bending rollers carried by the carriage is possibleby pressing together the connection which is in the manner of a tensionspring.

In order to ensure that the sheet metal part is already fixed rigidly tothe profile body before the start of the bending process, it isexpedient to provide the counter support at a greater distance from thecarriage than the bending rollers, such that when lifting the carriagethe counter support firstly comes into contact with the sheet metal partand is pressed against the profile body by means of said countersupport, before the bending rollers, which are also connected to thecarriage, come into contact with the sheet metal part.

In an expedient development, on one pressing side facing the profilebody, the counter support has a counter profile configured in the mannerof a bending profile which is identical to the bending profile of theprofile body in the region of the initial contact point, at which thecounter support presses the sheet metal part against the profile body.The counter support serves to form the sheet metal part in the region ofthe initial contact point according to the bending profile of theprofile body by pressing together the counter support with the profilebody.

In a development of the invention, the profile body is designed as apiston roller, for example for a radial piston engine or a radial pistonpump with a roller profile, against which the sheet metal part providedas a seat plate for the piston roller on a piston, may be pressed usingthe bending rollers. In the profile body designed as a piston roller, itis expedient to press the sheet metal part by means of two bendingrollers against the roller profile. The bending rollers press the sheetmetal part by lifting the carriage—proceeding from the initial contactpoint and running in the opposing direction—along the roller profileagainst the piston roller.

Expediently, the bending rollers are connected to one another via atension spring which is dimensioned such that pressing the sheet metalpart against the piston roller by lifting the carriage over the entireroller profile of the piston roller may be carried out withapproximately uniform bending stress.

An embodiment of the invention is described in more detail hereinafterwith reference to the drawings, in which:

FIG. 1 shows a diagrammatic construction of the bending device with asheet metal part provided for forming,

FIG. 2 shows the bending device according to FIG. 1 at the start of thebending process,

FIG. 3 shows the bending device according to FIG. 1 in the middle of thebending process,

FIG. 4 shows the bending device according to FIG. 1 at the end of thebending process,

FIG. 5 shows a cross section through a cylinder block of a radial pistonengine and

FIG. 6 shows a cross section through a cylinder according to FIG. 5 witha piston and a bearing for a piston roller coupled thereto.

FIG. 1 shows a bending device 22 with a profile body 24 and bendingrollers 26, 28 fixed via a fixing device, not shown, which are mountedon supports 30, 32 on a carriage 34. The bending rollers 26, 28 arearranged via chassis 36, 38 provided on the supports 30, 32 on thecarriage 34 and which may be moved counter to an arrow directionidentified by an arrow 40 in FIG. 1. The bending rollers 26, 28 areacted upon in the manner of a tension spring via a tension spring 42provided on the supports 30, 32. On the carriage 34 a counter support 44is arranged via a compression spring 46, which acts on the countersupport 44 in the direction of the arrow indicated by an arrow 48, whichis located at right angles to the direction of the arrow 40.

Between the profile body 24 and the bending rollers 26, 28 as well asthe counter support 44, a sheet metal part 50 provided for the formingis positioned which is pressed via the counter support 44 at an initialcontact point 54 against the profile body 24 and may be pressed via thebending rollers 26, 28 against a bending profile 52 of the profile body24 designed to be circular in this embodiment. The counter support 44comprises on one pressing side 56 facing the profile body 24 a counterprofile 58, the shape thereof corresponding to the shape of the bendingprofile 52 of the profile body 24 at the initial contact point 54.

FIG. 1 shows the sheet metal part 50 in a position pressed against theprofile body 24, the carriage 34 already having being lifted in thedirection of the arrow 48, so that in addition to the counter support 44the bending rollers 26, 28 which are arranged on opposing sides of thecounter support 44 on the carriage 34, are in contact with the sheetmetal part 50. By lifting the carriage 34 further in the direction ofthe arrow 48, the sheet metal part 50 is pressed against the profilebody 24. A right-hand portion 60 of the sheet metal part 50 is pressedby means of the bending roller 26 against the profile body 24 and, bylifting the carriage 34 with the bending roller 26, is adapted to thebending profile 52 of the profile body 24 as far as a sheet metal partend 62 on the right-hand portion 60, by plastic forming of the sheetmetal part 50. In contrast thereto, the bending roller 28 presses aleft-hand portion 64 opposing the right-hand portion 60 of the sheetmetal part 50 as far as a sheet metal part end 66 on the left-handportion 64 against the bending profile 52 of the profile body 24.

FIGS. 2, 3 and 4 show the bending process of the sheet metal part 50 atthe start of the bending process (FIG. 2), in the middle of the bendingprocess (FIG. 3) and at the end of the bending process (FIG. 4).

FIG. 2 shows the sheet metal part 50 slightly bent in the direction ofthe arrow 48, the carriage 34 being lifted such that the outer surfaces68, 70 of the bending rollers 26, 28 have already been lifted away overthe pressing side 56 of the counter support 44 in the direction of thearrow 48. The counter support 44 fixes the sheet metal part 50 to theprofile body 24 and at the same time prevents the sheet metal part 50from buckling at the initial contact point 54, as a result of bendingstresses which are exerted by the bending rollers 26, 28, by lifting thecarriage 34 onto the sheet metal part 50. The sheet metal part 50 isadditionally pressed against the profile body 24 by the counter profile58 provided on the counter support 44, and at the initial contact point54, and formed according to the bending profile 52 of the profile body24.

At the start of the bending process, a spring force F_(Spring) which isidentified in FIGS. 2, 3 and 4 by an arrow, only has a comparativelysmall portion of a normal force F_(Normal), generating the compressivestress and identified in FIGS. 2, 3 and 4 by an arrow, for the localplastification of the sheet metal part 50. At the start of the bendingprocess, the normal force F_(Normal) is largely applied by a liftingforce F_(Stroke) generated by lifting the carriage 34.

FIG. 3 shows the bending device 22, in which the sheet metal part 50 islocated in the middle of the bending process, and has already beenpressed against the profile body 24 as far as just before the sheetmetal part ends 62, 66. In contrast to the start of the bending process,the normal force F_(Normal) is divided in half in the middle of thebending process, as shown in FIG. 3, respectively into the spring forceF_(Spring) produced by the tension spring 42 and the lifting forceF_(Stroke) of the carriage 34.

At the end of the bending process, which is shown in FIG. 4, thecarriage 34 is lifted in the direction of the arrow 48 such that thebending rollers 26, 28 have pressed the entire sheet metal part 50against the profile body 24 and are located at the sheet metal part ends62, 66 of the sheet metal part 50. In the portion which the bendingrollers 26, 28 have covered between the position shown in FIG. 3 and theposition shown in FIG. 4 of the bending rollers 26, 28 on the sheetmetal part 50, the spring force F_(Spring) produced by the tensionspring 42 predominates over the lifting force F_(Stroke) of the carriage34 to produce the compressive stresses between the bending rollers 26,28 and the sheet metal part 50. The spring force F_(Spring) corresponds,therefore, approximately to the normal force F_(Normal) for the localplastification of the sheet metal part 50 and, as a result, compensatesfor the comparatively low portion of lifting force F_(Stroke) of thecarriage 34.

The combination of the lifting force F_(Stroke) produced by lifting thecarriage 34 and the spring force F_(Spring) produced by the tensionspring 42 placing the bending rollers 26, 28 under tensile load relativeto one another allows a particularly accurate forming of the sheet metalpart from the initial contact point as far as the sheet metal part ends,along the entire bending profile of the profile body and with uniformbending stress exerted on the sheet metal part.

The invention is not limited to the embodiment shown in the drawings, inparticular not limited to a profile body which is configured as a pistonroller with a cylinder shell profile. All the features described aboveand shown in the drawings may be combined with one another in anymanner.

1. Method for bending a sheet metal part on a profile body comprising abending profile, the sheet metal part being pressed against the profilebody at an initial contact point, and bending rollers pressing the sheetmetal part along the bending profile against the profile body andplastically adapting to the shape of the profile body.
 2. Methodaccording to claim 1, wherein the bending rollers mounted on a carriageare pressed against the sheet metal part by lifting the carriage. 3.Method according to claim 2, wherein the bending rollers, rotatablymounted on a single axis, are guided by further lifting of the carriageon the profile body along the bending profile.
 4. Method according toclaim 2, wherein by lifting the carriage carrying the bending rollers ina single step for pressing the sheet metal part against the profile bodyand for adapting the sheet metal part to the shape of the profile body.5. Method according to claim 2, wherein the sheet metal part before thestart of the bending process at the initial contact point is pressedagainst the profile body by a counter support mounted on the carriageand is held during the bending process at the initial contact point. 6.Bending device for bending a sheet metal part on a profile bodycomprising a bending profile, with a carriage arranged at a variabledistance therefrom, on which bending rollers connected to one another inthe manner of a tension spring are mounted for pressing the sheet metalpart at an initial contact point and along the bending profile of theprofile body.
 7. Bending device according to claim 6, wherein bendingstresses exerted by the bending rollers on the sheet metal part areapproximately uniform during a complete bending process.
 8. Bendingdevice according to claim 6 wherein the carriage is configured to beable to be lifted vertically relative to the sheet metal part. 9.Bending device according to claim 6, further comprising supports whichare movably arranged on the carriage for guiding the bending rollersmounted on a single axis thereon along the bending profile.
 10. Bendingdevice according to claim 6, wherein the profile body is fixed. 11.Bending device according to claim 6, further comprising a countersupport for pressing the sheet metal part against the initial contactpoint of the profile body.
 12. Bending device according to claim 11,wherein the counter support is connected to the carriage in the mannerof a compression spring.
 13. Bending device according to claim 12,wherein the counter support is provided with a pressing side facing thesheet metal part and, in the unloaded state of the compression spring,is at a greater distance from the carriage than the bending rollerswhich are mounted on the carriage via the supports.
 14. Bending deviceaccording to claim 13, wherein the counter support on the pressing sidecomprises a counter profile which is identical to the bending profile ofthe profile body in the region of the initial contact point.
 15. Bendingdevice according to claim 6, wherein the profile body is designed as apiston roller in the manner of a cylinder, which is provided for aradial piston machine.
 16. Bending device according to claim 11, furthercomprising two bending rollers coupled to one another by a tensionspring.